Contact assembly having hinge means utilizing electrodynamic forces of current flow therethrough



Nov. 24, 1964 WIKTOR 3,158,720

CONTACT ASSEMBLY HAVING HINGE MEANS UTILIZING ELECTRODYNAMIC FORCES OFCURRENT FLOW THERETHROUGH 5 Sheets-Sheet 1 Filed Feb. 17. 1961 NVENTORDOM/N/K W/KTOP.

Nov. 24, 1964 D. WIKTOR CONTACT ASSEMBLY HAVING HINGE MEANS UTILIZINELECTRODYNAMIC FORCES OF CURRENT mow THERETHROUGH 5 Sheets-sheet 2 FiledFeb. 17. 1961 JNVENTOR. DOM/MK W//( 702 A TTORNEY Nov. 24, 1964 CONTACTASSEMBLY l-IAVING HI D WIKTOR NGE MEANS UTILIZING ELECTRODYNAMIC FORCESOF CURRENT Filed Feb. 17, 1961 FLOW THERETHROUGH 3 Sheets-Sheet 3INVENTOR. DOM/N/K W/KTOR Adm ATTORNEY United States Patent 3,158,720CONTACT ASSEMBLY HAVING HINGE MEANS UTILIZING ELECTRODYNAMIC FORCES OFCURRENT FLOW THERETHROUGH Dominik Wiktor, Irvington, N.J., assignor toFederal Pacific Electric Company, a corporation of Delaware Filed Feb.17, 1961, Ser. No. 89,977 6 Claims. (Cl. 200-146) This invention relatesgenerally to power circuit breakers and more particularly to the movingcontact assembly for such apparatus.

Each pole of an illustrative multipole circuit breaker that is describedin detail below includes a moving contact arm that carries main andarcing contacts into and out of substantially normal contact engagementwith companion contacts. The arcing contacts are designed to part fromcompanion stationary arcing contacts only after the main moving contactarm has separated from its companion contact. Similarly, the arcingcontacts engage their companion contacts before the main contacts toucheach other during the closing operation.

An object of the present invention resides in the provision of animproved arrangement for providing a mechanical pivotal support for thecontact arm of a novel form that is highly effective in makinglow-resistance electrical connection to the contact arm.

Another object of this invention resides in the provision of a movingcontact assembly having means for providing high contact pressurebetween the pivot of the contact arm and its support, so as to providelow contact resistance not only under short-circuit conditions, but alsounder normal load-current conditions and during contactopeningoperations.

A further object of the invention relates to improvements in themounting and spring-biasing of arcing contacts on a pivoted contact arm.It is customary for arcing contacts to extend up into an arc chute, andin usual arrangements there is a blow-off electrodynamic force thattends to reduce arcing-contact pressure and to lift the arcing contactprematurely away from its companion contact during opening of thecircuit breaker. A feature of the invention resides in the provision ofheavy spring biasing means for the arcing contacts in a novelarrangement, wherein the hinge or pivotal connection of the contact armis also improved. Moreover, despite this relationship between hingecontact pressure and arcing-contact pressure, means is provided forindependently augmenting the hinge contact pressure without developingexcessive arcing-contact pressure such as would impose an excessivemechanical load on the contact-closing mechanism.

The illustrative embodiment of the invention, which has been generallyreferred to above as incorporating the various novel features of theinvention, is more fully described in the remainder of thisspecification, from which further novel features, objects and advantageswill become apparent. In the following description, reference is made tothe accompanying drawings forming part of this disclosure.

In the drawings:

FIG. 1 is a side elevation of an illustrative circuit breaker embodyingfeatures of the invention;

FIG. 2 is a front elevation of the apparatus in FIG. I viewed from theleft thereof, with portions omitted and other portions broken away; and

FIG. 3 is a view similar to FIG. 1, of the moving contact assembly of asingle pole, including main and arcing contacts, the parts being shownwith the arcing contacts touching and the main contacts parted.

Referring now to the drawings, a frame is shown bearing three blocks 12of insulation. Each book supports the stationary and movable contacts ina respective 3,158,720 Patented Nov. 24, 1964 pole of the three polesillustrated. Each pole has a pair of rearwardly projecting terminals 14and 16. Terminal 14 extends through the block of insulation to the frontthereof where it bears stationary arcing contacts 18. A number ofside-by-side main contact members 22 are confined between a pair of sideplates 24. Hinge ends 26 of the main contact members 22 are biased bysprings 28 into a groove in terminal 14.

When the circuit breaker is closed as illustrated in FIG. 1, maincontact members 22 are forcibly displaced to the right against theircompression springs 28 by the cooperating movable main contact 30. Whencontact arm 30 is operated to the left (as described in further detailbelow) so as to open the circuit breaker, compression springs 28 drivemain contact members 22 clockwise about their hinge ends 26. Ears 32 ofcontact members 22 limit their counterclockwise movement by engagementwith stationary pin 34 (FIG. 3) supported between side plates 24, and inthis way these contacts are under substantial spring bias from theinstant of engagement of contact arm 30 with contact members 22.

Terminal 16 provides a conductive path through block 12 and throughtwo-turn over-current coil 36, forward through a hinge block 38 tomovable contact arm 30. Cooperating with the over-current coil 36 ismovable armature 37 and associated structures whose details areunnecessary to an understanding of the present invention.

Movable contact arm 30 is formed of a pair of vertical bars 30a brazedto and thus united by a horizontal part 30b. Contact arm 30 has a pairof laterally spaced hooks 40 (see also FIG. 3) that are received inslots 42 formed in block 38, one for each hook 40. (See the left-handpole in FIG. 2.) A shaft 46 is united to block 38 and extends across theslots 42 in which hooks 40 are received. A slot 44 is formed in contactarm 30 adjacent the base of hook 40. The top and right-hand surfaces ofslot 44 diverge and provide contact engagement along two arcuatelyspaced lines of contact along shaft 46. Members 30, 38, and 46, are ofcopper, advantageously silver-plated, and form a hinge connection ofextremely low resistance and high current capacity. Contact pressure ismaintained between moving contact arm 30 and shaft 46 by a pressure roll48 and a spring bias means to be described.

The conductivity of the hinge joint is excellent during normalconditions when currents of the order of one or two thousand amperes maybe carried. However, when short-circuit current peaks are to be carried,the pressure between moving contact arm 30 and the hinge shaft 46 isgreatly increased by virtue of the geometry of the conductors providingthe main current path through the circuit breaker. There is a broadcurrent loop extending horizontally through terminal 14, downwardthrough the main contacts 22 and contact arm 30, and horizontallythrough terminal 16. This loop provides electrodynamic force tending toshift moving contact arm 30 to the left. Contact arm 30 thus tends topivot clockwise about a mechanical operating pivot 75 (described below),building up the contact pressure of moving contact arm 30 against shaft46. This tendency of member 39 to move to the left in FIG. 1 is resistedby the hooks 40 extending about shafts 46. Consequently, it is safe fornotches defined by hooks 40 and the opposite portion 41 of arm 30 toopen outwardly of the current loop through parts 14, 22, and 16.

The movable contact arm 30 in each pole bears a pair of laterallyseparated movable arcing contacts 50 which cooperate with stationaryarcing contacts 18. The lateral separation between the arcing contacts50 is maintained by suitably shaped insulating spacer 66 (FIG. 2).Rocker member or lever 62 is carried on pivot pin 70 which passesthrough moving contact arm 30. Arcing contacts 18 and 50 engage at apoint spaced vertically above the main contacts 22 and 30, the arcingcontacts 50 extending well up into an arc chute 51 only part of which isshown. In the closed condition of the circuit breaker as illustrated inFIG. 1 and even when main contacts 22 and 30 are parted (FIG. 3) arcingcontacts 50 are biased against stationary arcing contacts 18 bycompression springs 52 which press against shoes 54 pivoted by pins 56to the arcing contacts 50. Coil springs 52 are guided on rods 58 whichare secured at one end to shoes 54. Insulated bushings 59 are interposedbetween the springs 52 and the shoes 54 to inhibit the flow of currentthrough the springs. Rods 54 work slidably in suitable bores in a shaft60 that is rotatably mounted in rocker member 62. Each of the arcingcontacts 50 is biased clockwise by a spring 52, and pivots about a hingecontact pin 64, which is received in moving contact arm 30.

The reaction of the upward pressure by springs 52 against arcing contact50 is applied to rocker member 62 in a manner that also develops heavybias of roller 48 against shaft 46. The short lever arm between roller48 and pivot pin 70 provides mechanical advantage that magnifies theforce applied to shaft 46 by the springs 52 which act on the longerlever arm between the axis of shaft 60 and pivot pin 70. This bias onroller 48 provides normal operating contact pressure at the main hingecontact 40, 46 of the movable contact arm 30 this pressure being at itsmaximum in the contact closed or on position.

Compression springs 72 act between portions of members 30 and 62 wellabove pivot pin 79, to augment the pressure developed by springs 52between elements 40 and 46 when the circuit breaker is closed, and toprovide hinge contact presstu'e when the circuit breaker is open andsprings 52 no longer apply bias to rocker 62. The pressure of springs 72assures proper mechanical pivoting operation of the contact arm at timeswhen the arcing contacts are disengaged and it also provides goodelectrical contact at hinge 40, 46 when the contacts are being opened.This is an important concern in the event that the circuit breaker istripped open to interrupt currents of short-circuit magnitude, 50,000amperes for example. This augmented hinge contact pressure is producedwithout correspondingly increasing the clockwise bias acting on thearcing contacts 50. Any excessive increase in the arcing-contact biasbeyond the value needed for establishing normal operating contactpressure would unnecessarily increase the force required to close thecircuit breaker.

Shaft 75 extends laterally beyond both side faces of moving contact arm3%) and into the U-shaped member 76 carried by the common bar '78 whichoperates all of the contact arms and the arcing contacts of all threepoles of the circuit breaker. The bar 78 and U-shaped members 76 form adriving link for moving the contact arms 36 between the open and closedpositions thereof. An exemplary mechanism for operating bar 78 isdescribed in my copending application Serial No. 101,314, filedconcurrently herewith (now Patent No. 3,097,275), both applicationshaving a common assignee.

When the circuit breaker is open, movable arcing contact 50 is spacedwell away from stationary arcing contact 13. At this time, clockwisedisplacement of arcing contact 50 relative to contact arm 30 due to theclockwise bias of spring 52 is adjustably limited by nut 74. When thecircuit breaker is in its closed configuration as illustrated in FIG. 1,nut or stop 74- has a small but definite separation from shaft 60. Thisspacing is made large enough to insure counterclockwise travel of movingcontact arm 36 through a sufficient angle in an opening stroke to allowcar 32 of main contact members 22 to be arrested by pin 34 and for adefinite separation to be developed between the main contactsrepresented by members 22 and contact arm 30. Thereafter, duringcontinued contact-opening travel of moving contact arm 30, shaft 60comes into engagement with stop 74, as shown in FIG. 3. From this pointon, operation of tie bar 78 in the opening direction provides positivedrive to separate each arcing contact 50 from its companion stationaryarcing contact 18.

It may now be considered that the circuit breaker is open or at anintermediate position with the main and arcing contacts parted, ratherthan in the closed condition shown. In the parted-contacts condition,springs 52 and 72 (there being two of each at each pole) bias rockermember 62 counterclockwise about pivot and thereby develop relativelyheavy pressure of roller 48 against shaft 46. The reaction forceresulting at shaft 70 in contact arm 30 acts to force hooks 4d of themoving contact arm 30 against the face of shaft 46 opposite roller 48.

When the circuit breaker is open and is to be closed, tie bar 78 isshifted to the right and the shafts of the several poles are swungclockwise in unison about the common axis of respective shafts 46. Themoving arcing contacts 50 in each pole engage companion contacts 18, andnuts 74 are lifted from shafts 60 as shafts 75 continue their travel tothe right. Thereafter, the moving contact arm 30 engages its companioncontact members 22 in each of the three poles of the circuit breaker.Drive of tie bar 78 continues for a short distance after initialengagement of the main contacts 22 and 30, building the contact pressureup by shifting main contact 22 to the right, and increasing thecompression that is maintained initially in springs 28 by ears 32 andpin 34.

High hinge contact pressure is maintained at book 40 and shaft 46 ofeach contact arm 30, both when the circuit breaker is closed and whenthe contacts are being opened. Springs 52 function for the dual purposesof establishing arcing-contact pressure and for biasing lever 62 so asto force roller 48 against shaft 46 and thereby to develop strongcontact pressure between the hinge elements 4t) and 46 of the contactarm 30. Hinge contact pressure is augmented by springs 72. These springsprovide the only spring bias for the hinge at times when arcing contacts50 are out of contact with contacts 18.

The term circuit breaker as used in this application ap plies toapparatus intended to carry high currents and to interrupt currents ofshort-circuit magnitude; and accordingly the term circuit breaker isused in a generic sense, to apply also to switches having similar dutyre quirements.

The foregoing represents the presently preferred form in which thevarious aspects of the invention may be applied. However, variousmodifications will readily occur to those skilled in the art, andtherefore, the invention should be broadly construed in accordance withits full spirit and scope.

What I claim is:

l. A circuit breaker including first and second terminal members, amovable contact arm, a companion contact mounted on said first terminalmember, said contact arm being pivotally mounted on said second terminalmember for movement from a closed position abutting said companioncontact to an open position, a driving link connected to said arm formoving said arm between said open and said closed position, a currentloop being formed by said terminals, said companion contact and saidcontact arm in its closed position, said second terminal being providedwith a hinge element including a hinge shaft, said contact arm beingprovided with a complementary hinge element partially encompassing saidshaft and providing electrical connection and mechanical articulationthereto, said complementary hinge element having an opening formedtherein directed away from said current loop, said hinge elements beingdriven together in a given direction by electrodynamic forces due tohigh currents flowing in said loop, and spring means normally biasingsaid hinge elements together in said given direction.

2. A circuit breaker including first and second terminal members, amovable contact arm, a companion contact mounted on said first terminalmember, said contact arm being pivotally mounted on said second terminalmember for movement from a closed position abutting said companioncontact to an open position, a driving link connected to said arm formoving said arm between said open position and said closed position, acurrent loop being formed by said terminals, said companion contact andsaid contact arm in its closed position, said second terminal beingprovided with a hinge element including a hinge shaft, said contact armbeing provided with a complementary hinge element partially encompassingsaid shaft, said complementary hinge element having an open ing formedtherein directed away from said current loop, said hinge elements beingdriven together in a given direction by electrodynamic forces due tohigh currents flowing in said loop, and spring means normally biasingsaid hinge elements together in said given direction, said spring meansapplying biasing force to said shaft portion exposed at the opening insaid complementary hinge element.

3. A circuit breaker including first and second terminal members, amovable contact arm, a companion contact mounted on said first terminalmember, said contact arm being pivotally mounted on said second terminalmember for movement from a closed position abutting said companioncontact to an open position, a driving link connected to said arm formoving said arm between said open and said closed position, a currentloop being formed by said terminals, said companion contact and saidcontact arm in its closed position, said second terminal being providedwith a first hinge element, said contact arm being provided with acomplementary hinge element, said hinge elements being driven togetherin a given direction by electrodynamic forces due to high currentsflowing in said loop, and spring means normally biasing said hingeelements together in said given direction, said spring means including alever pivotally mounted on said contact arm and bearing against saidfirst hinge element and a spring reacting between said lever and saidcontact arm.

4. A circuit breaker including first and second terminal members, amovable main contact arm, an arcing contact arm pivotally mounted onsaid main contact arm, companion main and arcing contacts, respectively,mounted on said first terminal member, said contact arm being pivotallymounted on said second terminal member for movement from a closedposition wherein said main contact arm and said arcing contact arm abuttsaid respective companion contacts to an open position, a driving linkconnected to said arm for moving said arm between said opened positionand said closed position, a main current loop being formed by saidterminals said companion main contact and said main contact arm in itsclosed position, said second terminal being provided with a hingeelement, said main contact arm being provided with a complementary hingeelement, said hinge elements being driven together in a given directionby electrodynamic forces due to high currents flowing in said loop,first spring means normally biasing said hinge elements together in saidgiven direction, said spring means including a lever pivotally mountedon said contact arm and bearing against said hinge element and a springreacting between said lever and said contact arm, and second springmeans between said arcing contact arm and said lever further biasingsaid hinge elements together in said given direction in the closedposition of said contact arms.

5. A circuit breaker including first and second terminal members; amovable main contact arm; an arcing contact arm pivotally mounted onsaid main contact arm; companion main and arcing contacts, respectively,mounted on said first terminal member; said contact arm being pivotallymounted on said second terminal member for movement from a closedposition wherein said main contact arm and said arcing contact arm abuttsaid respective companion contacts to an open position; a driving linkconnected to said arm for moving said arm between said opened positionand said closed position; a main current loop being formed by saidterminals, said companion main contact, and said main contact arm in itsclosed position; said second terminal being provided with a hingeelement; said main contact arm being provided with a complementary hingeelement; said hinge elements being driven together in a given directionby electrodynamic forces due to high currents flowing in said loop;first spring means normally biasing said hinge elements together in saidgiven direction, said first spring means including a lever pivotallymounted intermediate its ends on said main contact arm and forming longand short lever arms, the end of said short arm operatively bearingagainst said hinge element, and a spring reacting between said longlever arm and said main contact arm; second spring means between saidarcing contact arm and said long lever arm further biasing said hingeelements together in said given direction in the closed position of saidcontact arms.

6. A circuit breaker including a back plate, a pair of substantiallyparallel terminals extending through said back plate, and switchingmeans at one side of said back plate extending from one of saidterminals to the other when closed, said terminals and said switchingmeans constituting a current loop that creates strong loopexpandingforces electrodynamically during short-circuit current conditions, saidswitching means including a contact arm having a mechanical andelectrical hinge connection to one of said terminals, said hingeconnection including a shaft and a bearing on said shaft, certain areasof said shaft and said bearing being forced together by saidloop-expanding forces, and spring biasing means acting between saidshaft and said bearing and arranged to provide contact pressure at saidareas even in the absence of said loop-expanding forces.

References Cited in the file of this patent UNITED STATES PATENTS1,749,200 Van Valkenburg Mar. 4, 1930 2,329,003 Seaman Sept. 7, 19432,581,181 Favre Jan. 1, 1952 2,627,559 Netzel Feb. 3, 1953

1. A CIRCUIT BREAKER INCLUDING FIRST AND SECOND TERMINAL MEMBERS, AMOVABLE CONTACT ARM, A COMPANION CONTACT MOUNTED ON SAID FIRST TERMINALMEMBER, SAID CONTACT ARM BEING PIVOTALLY MOUNTED ON SAID SECOND TERMINALMEMBER FOR MOVEMENT FROM A CLOSED POSITION ABUTTING SAID COMPANIONCONTACT TO AN OPEN POSITION, A DRIVING LINK CONNECTED TO SAID ARM FORMOVING SAID ARM BETWEEN SAID OPEN AND SAID CLOSED POSITION, A CURRENTLOOP BEING FORMED BY SAID TERMINALS, SAID COMPANION CONTACT AND SAIDCONTACT ARM IN ITS CLOSED POSITION, SAID SECOND TERMINAL BEING PROVIDEDWITH A HINGE ELEMENT INCLUDING A HINGE SHAFT, SAID CONTACT ARM BEINGPROVIDED WITH A COMPLEMENTARY HINGE ELEMENT PARTIALLY ENCOMPASSING SAIDSHAFT AND PROVIDING ELECTRICAL CONNECTION AND MECHANICAL ARTICULATIONTHERETO, SAID COMPLEMENTARY HINGE ELEMENT HAVING AN OPENING FORMEDTHEREIN DIRECTED AWAY FROM SAID CURRENT LOOP, SAID HINGE ELEMENTS BEINGDRIVEN TOGETHER IN A GIVEN DIRECTION BY ELECTRODYNAMIC FORCES DUE TOHIGH CURRENTS FLOWING IN SAID LOOP, AND SPRING MEANS NORMALLY BIASINGSAID HINGE ELEMENTS TOGETHER IN SAID GIVEN DIRECTION.